1. Technical Field
The present system and method generally relate to load coils, and more particularly to an xDSL (Digital Subscriber Line) compatible load coil for conditioning POTS (Plain Old Telephone Service)-band signals while permitting xDSL signals to traverse the load coil with low attenuation.
2. Description of Background Art
Load coils, also referred to as “loading coils,” are conventionally positioned along long local loops to improve POTS, or voice-grade, communications over the loop. Conventional load coils are inductive devices that are positioned along a local loop to compensate for, or counteract, the distributed parallel capacitance of the local loop. Such use of load coils generally conditions long local loops for POTS-band communications by flattening out the POTS band up to about 3.6 KHz. These load coils, however, also significantly limit, or prevent, the provision of digital services over a loaded loop due to the attenuation conventional load coils impart to higher frequency signals, such as ADSL (Asymmetric DSL) signals.
ADSL signals, for example, typically reside between about 26 KHz-1.1 MHz and are highly attenuated by conventional load coils. Indeed, in the past, load coils are routinely removed from local loops in order to provide ADSL service over such loops. The removal of such load coils, in turn, impairs or prevents the provision of POTS service over long loops, such as over loops longer than about 18,000 feet.
A need exists, therefore for an improved load coil that compensates for the distributed parallel capacitance of a local loop while permitting passage of higher frequency digital signals.
Additional background details regarding DSL technology more generally are described in Understanding Digitial Subscriber Line Technology by Starr, Cioffi, and Silverman, Prentice Hall 1999, ISBN 0137805454 and in DSL—Simulation Techniques and Standards Development for Digital Subscriber Line Systems by Walter Y. Chen, Macmillan Technical Publishing, ISBN 1578700175, the disclosures of which are hereby incorporated by reference.